Its there so you (and especially your passenger) can see stuff in the center stack at night withough having to turn on the map lights and affect the driver's vision.

Our 02 A4 had them too...they're actually nice to have...makes it easy for my wife to find stuff like the cup in the cupholder or something inside the console.

Chalk it up to Nissan seeing that premium branded cars like Audi have these, therefore there must be a logical and useful reason for them to exist so we need to have them too...without ever knowing the real reason they're there. Kind of like the Burger King branch location strategy...let McDonalds do all the market research and analysis and then just put up a BK near the McDonalds.